.308 cartridge headspace question???

I have read posts here and on other forums but I'm still not getting it. I purchased one of those Hornady cartridge headspace/clearance kits to set my FL sizing die up with and my measurements on once fired brass (my bolt rifle) vary from 1.624 to 1.632 with the average being 1.627. My dial caliper is spot on in that it measures the kit at exactly 2" every time.

Do I just take the average and set my die up to bump the shoulder back to 1.625 or do I take the shortest measurement and bump 'em all back to that less .002? I would have thought the brass would be more consistent (Remington) being it's formed in my rifle but what do I know.

If there is a thread that answers this please point me towards it.

What you're seeing is that the once-fired brass hasn't fully formed to the chamber. Not unusual. What I'd do is take the longest case and bump the shoulder a thousandth (less than .002" anyway) and size all the cases at that setting. Write down the number so that after the second firing you can remeasure and see if the cases are still growing to fill the chamber. If so, repeat the process. Usually I find the longest cases from the first firing are pretty close and if a second die adjustment is needed it's just a couple thousandths.

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Originally Posted by TC260

What you're seeing is that the once-fired brass hasn't fully formed to the chamber. Not unusual. What I'd do is take the longest case and bump the shoulder a thousandth (less than .002" anyway) and size all the cases at that setting. Write down the number so that after the second firing you can remeasure and see if the cases are still growing to fill the chamber. If so, repeat the process. Usually I find the longest cases from the first firing are pretty close and if a second die adjustment is needed it's just a couple thousandths.

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Exactly. 308 often takes two to three loads to fully fireform.

Thanks, for the answer to my question. I was beginning to think my caliper was failing, even though it keep zeroing on the kit consistently.

Sitting Duck,
You are depriming the cases before you measure them, right? If not, sometimes you get enough primer protrusion or flash around the primer strike to throw your measurements off. I don't shoot .308, but on my "308 family" cases (243, 260, 7mm08) first time fired brass, I rarely get 8 thousandths difference - more like 1-3 thousandths.....but every rifle is different...
Elkbane

The more times fired the harder your brass gets and the less consistency you will see in your fired headspace length and consistency in your sized headspace length as well. Lubing your necks inside and out if you use a type die that has a neck sizing ball helps things as does using a quality case lube in similar amounts on each piece of brass.

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Originally Posted by stangfish

The more times fired the harder your brass gets and the less consistency you will see in your fired headspace length and consistency in your sized headspace length as well. Lubing your necks inside and out if you use a type dai that has a neck sizing ball helps things as does using a quality case lube in similar amounts on each piece of brass.

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What he said....

I can't ever recall having a much variation as you're seeing but after 2 to 4 firings & a good annealing at the 2nd firing they usually settle down. I like to use Rem brass as it seems to last longer than Win or Fed & it's not as pricey as Lapua, etc.
Lastly, to touch on what Stang said, don't be stingy with the lube. I find my 30.06 cases get a little "draggy" when I don't use enough lube. When the press handle is a little harder that usual, the case come out in assorted lengths & occasionally bent. Too bent for me to want to use them & expect any accuracy.

On the lube issue, just make sure to not get too generous with it in the shoulder/neck area, or it will cause hydraulic lock, in which case the brass, being the softest thing in the mix, will dent, big time.

....and keep your vent hole in your die neck clean and free. Otherwise what handi says will come to fruition.

I haven't decapped the brass so maybe that plays into my readings. I will do that and bump the longest back .001, reload and shoot the puppies. Thank you, one and all for the advice.

Either deprime the cases or reseat them below flush before you measure. I always reseat them as that does not alter the case body in any way before you measure. Luckus

I've always used a universal depriming die. Hadn't thought about reseating fired primers in the absence of a depriming die. That's a good little trick to know.